1. Field of the Invention
The present invention relates to a position indicator whose rotation angle with respect to an axial direction can be detected, a circuit component used in the position indicator, and an input device having the position indicator.
2. Description of the Related Art
In recent years, input devices which operate based on electromagnetic resonance technology have been used as input devices for a personal computer and the like. Such input devices generally comprise a pen-like position indicator and a position detecting device having an input surface, on which an input operation is performed using the position indicator. An input operation using the position indicator may include, for example, a pointing operation, a handwritten character input operation, or a hand-drawn illustration input operation.
Among these input devices, there is a kind of input device on which not only a pointing operation, a handwritten character input operation, and the like, can be performed, but also rotation and tilt of the position indicator can be input as data depending on how the position indicator is held and how the position indicator is twisted by the hand of a user.
An example of such a kind of the input device is disclosed in Japanese Unexamined Patent Application Publication No. H08-30374 (referred to as “Patent Document 1” hereinafter). The input device disclosed in Patent Document 1 includes a position indicator having two cylindrical magnetic cores. The two magnetic cores are disposed so that a midpoint thereof is matched with a bar-like rod (providing a pen-tip at its distal end) of the position indicator.
A control coil is wound around one of the two magnetic cores. Further, a transmission coil is wound around the two magnetic cores so that the two magnetic cores are bundled together. The transmission coil and a capacitor constitute a resonant circuit. Further, by controlling the opening/closing of the control coil, distribution of the magnetic flux passing through the transmission coil is changed, to thereby detect rotation angle and tilt angle of the position indicator.
Another example of the input device capable of detection rotation/tilt of the position indicator is disclosed in Japanese Unexamined Patent Application Publication No. H08-202489 (referred to as “Patent Document 2” hereinafter). The input device disclosed in Patent Document 2 includes a position indicator having two parallelepiped-shaped magnetic cores. The two magnetic cores are disposed so that they sandwich a pen-tip of the position indicator. When the two magnetic cores are combined, the axis in the longitudinal direction of the two magnetic cores is matched with the pen-tip.
Each of the magnetic cores has a control coil transversely wound therearound. Further, a transmission coil is transversely wound around the two magnetic cores so that the two magnetic cores are bundled together. The axis of the transmission coil, the position of the pen-tip, the axis of the position indicator, and the axis in the longitudinal direction of the two magnetic cores bundled together are all aligned with each other. Further, the input device includes a tablet, which has a detection circuit for detecting a tilt-detecting signal generated from the control coil(s), and a control circuit for determining the tilt angle of the position indicator based on the result detected by the detection circuit.
However, in the position indicator disclosed in Patent Document 1, since the two cylindrical magnetic cores are disposed side by side in a direction perpendicular to the axis of the position indicator, the position indicator has a relatively large outer diameter.
Further, when the bar-like rod (providing a pen-tip at its distal end) is passed through between the two magnetic cores, the two magnetic cores need to be sufficiently spaced apart from each other to prevent the rod, which passes therebetween, from interfering with the coil wound around each magnetic core. Thus, it was difficult to reduce the outer diameter of the position indicator. Still further, when the rod is not passed between the two magnetic cores, in order to connect the rod to a pen pressure detection switch provided at an end portion of the magnetic cores, to additionally detect the pen pressure, the rod has to be formed in a special (e.g., bent) shape, or an adapter has to be arranged between the rod and the switch.
Further, in the position indicator disclosed in Patent Document 2, in order to achieve a configuration capable of additionally detecting the pen pressure, a clearance greater than the diameter of the rod has to be provided between the two magnetic cores. Thus, a clearance of a predetermined size is formed between the two magnetic cores, thereby degrading the performance of the magnetic cores.